Heating, ventilation, and air conditioning management system and method

ABSTRACT

Systems and methods of controlling a heating, ventilating, and air conditioning system are provided that operate according to signals returned from return air temperature sensors as well as the supply air temperature sensors. Using predetermined temperature setpoints, return temperature information, and supply temperature information, the HVAC system is configured to maintain the temperature of a room first, by the use of its cooling valve, and second and only when the capacity of the cooling valve has peaked, by use of the fan. The presently disclosed improved HVAC system operates more efficiently by avoiding unit loading hopping and minimizing power consumption.

FIELD OF THE INVENTION

Embodiments of the present invention relate generally to field ofheating, ventilation, and air conditioning (HVAC) systems. Morespecifically, the invention relates to energy efficient HVAC systemsthat are used in commercial spaces.

BACKGROUND OF THE INVENTION

Modern heating, ventilation, and air conditioning (HVAC) systems areused in a wide range of environments for various purposes and are reliedupon in virtually every industry. These HVAC systems, for example, maybe used in single-family homes, multilevel office buildings, or evencomplex automated computer data centers spanning acres. Modern HVACsystems can provide ventilation, reduce air infiltration, and maintainpressure relationships between spaces in these environments.

At the same time, the costs of operating these systems may be very high.For example, the maintenance and electricity costs for a large HVACsystem, such as those used on computer data centers, may cost a companymillions of dollars. A typical one-megawatt data center may consume asmuch as 16 million kilowatt-hours of electricity a year, or theequivalent to the energy consumed by 1400 average U.S. households. Thetotal electric bill for computer servers and data centers has risen toover 100 billion kilowatt-hours of energy annually, costing roughly 7billion dollars in the US alone. By 2010, world data center electricityuse represented between 1.1 and 1.5 percent of world electricity use,while in the U.S., data center electricity use represented between 1.7and 2.2 percent of the total. At the same time, these servers and datacenters contribute to more than 0.5 percent of the total U.S. greenhousegas emissions, which is expected to double by 2020.

These high costs can largely be attributed to these large systems'inefficiencies. Remarkably, while modern HVAC systems may differ in sizeand power, the systems that are used in high-tech computer data roomsoperate largely in the same manner as those used in family homes. Evenmore extraordinary, the HVAC units that comprise a large HVAC system donot operate together as one would expect of a modern electronic system.These individual units are not controlled by a central controller orcomputer such that they would work together to maintain the air of theentire environment Instead, each operates independently to maintain theair of its individual space, often competing against each other inmanaging the temperature, humidity, and pressure in the room. Forexample, in a modern data room HVAC system, each HVAC unit controls itsfans and its cooling valves in response to only its own return airflowtemperature sensor readings and does not communicate with the otherunits or otherwise work with the other units to maintain the temperatureof the room.

This manner of operation results in tremendous inefficiency. The limiteduse of sensors compounded by the lack of direct communications withother HVAC units leads to uneven operations between the units, asituation called “load hopping.” For instance, one unit may be runningat full capacity while a neighboring unit runs at low capacity or sitscompletely idle. Moreover, it leads to constant activations,deactivations and adjustments by each HVAC unit as they each attempt,and often compete, to cool the room to the desired temperature. Theunits often overshoot the targeted temperature, causing other units toadjust incorrectly in response, resulting in a situation in which thereis an infinite loop of readjustments by the units, with the units neverhitting their targeted temperature. This causes uneven floor temperaturedistribution and localized supply air heating. Such a method results intremendously inefficient power-consumption rate and a greater rate ofHVAC unit component failures.

Accordingly, there is an important need for an improved method andsystem for controlling HVAC to operate more efficiently, particularly byavoiding load hopping and minimizing power consumption. A more efficientmethod and system for controlling HVAC systems may save corporations,and U.S. households alike, millions of dollars in total power costs eachyear and reduce greenhouse gas emissions.

SUMMARY OF THE INVENTION

The presently disclosed invention satisfies the above-described needs byintroducing systems and methods of controlling a heating, ventilating,and air conditioning system that operates according to signals returnedfrom its return air temperature sensors as well as the supply airtemperature sensors. By using both of these signals to control the fanspeed and the cooling valve openings and by prioritizing the use of thecooling valves over the use of the fans in order to reduce thetemperature of a room, these units, though independent from one another,act together to efficiently maintain the temperature and air quality ofthe entire environment. In addition, by controlling the cooling valvesbased, partly, on the supply air temperature, load hopping may beavoided.

In one aspect, embodiments of the present invention provide a method forconfiguring a heating, ventilation, and air conditioning system, thesystem including at least one HVAC unit, with each unit including acontrol circuit, and the method including the steps of receiving areturn air temperature signal at the control circuit at the at least oneHVAC unit; receiving a supply air temperature signal at the controlcircuit of the at least one HVAC unit; and controlling a fan and acooling value of the at least one HVAC unit based on the received returnair temperature signal and the received supply air temperature signal.

In one embodiment, the method further comprises the step of generating acooling valve drive signal according to at least one of return airtemperature signal and supply air temperature signal. In thisembodiment, the cooling valve may be controlled to increase the at leastone cooling valve's water output based on the higher of a cooling valvedrive signal between the return air temperature signal and the supplyair temperature signal. In another embodiment, the return airtemperature is compared with the supply air temperature signal and thecooling valve is controlled based on this comparison. At the same time,the fan may operate at a minimum speed based on the operations of thecooling valve, including its current operating capacity. In certaininstances, the fan may then be controlled to operate at a speed abovethe minimum speed. Specifically, this may occur when the cooling valveis operating at a maximum capacity.

In another aspect, a heating, ventilation, and air conditioning systemis provided, the system having at least one HVAC unit, with each HVACunit including: a fan, a cooling valve, and a processor that is coupledto least one fan and at least one cooling valve. The processor isadapted to execute instructions to receive a return air temperaturesignal at the control circuit at the at least one HVAC unit; receive asupply air temperature signal at the control circuit of the at least oneHVAC unit; and control the fan and the cooling valve of the at least oneHVAC unit based on the received return air temperature signal and thereceived supply air temperature signal.

In one embodiment, the system is further adapted to execute instructionsto generate a cooling valve drive signal according to at least one ofreturn air temperature signal and supply air temperature signal. Thecooling valve may then be controlled to increase its water output basedon the higher of the cooling valve drive signal between the return airtemperature signal and the supply air temperature signal.

In another embodiment, the return air temperature signal is comparedwith the supply air temperature signal. The cooling valve is thencontrolled based on the results of this comparison. At the same time,the fan may operate at a minimum speed based on the operations of thecooling valve, including its current operating capacity. In certaininstances, the fan may then be controlled to operate at a speed abovethe minimum speed, such as when the cooling valve is operating at amaximum capacity.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to facilitate a fuller understanding of the present invention,reference is now made to the accompanying drawings, in which likeelements are referenced with like numerals. These drawings should not beconstrued as limiting the present invention, but are intended to beexemplary only.

FIG. 1 is a flow chart illustrating an exemplary method of configuringand operating an efficient HVAC system.

FIG. 2 illustrates a floor plan of a data room utilizing the presentlydisclosed HVAC system.

FIG. 3 illustrates a floor plan of a data room utilizing the presentlydisclosed HVAC system that further contains a central computer.

FIG. 4 illustrates a block diagram of one exemplary HVAC unit of thepresently disclosed invention.

FIG. 5 is a flow chart illustrating an exemplary method for operating anHVAC unit.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the presently disclosed invention provide systems andmethods for a heating, ventilation, and air conditioning (HVAC) system.Specifically, to efficiently maintain the temperature and air quality ofan environment, the plurality of HVAC units of the system operatesaccording to signals returned from each unit's return and supply airtemperature sensors.

A method for configuring a heating, ventilation, and air conditioningsystem is provided in FIG. 1. The HVAC systems of the presentlydisclosed invention is configured to maintain the temperature of a room,first, by use of the cooling valves, and second and only when thecapacity of the cooling valve has peaked, by use of the fans. At step100, the HVAC units in the HVAC system are configured to receive areturn air temperature signal. This signal provides the temperature ofair entering each HVAC units. This temperature is likely to be theambient temperature of the room or the air near each unit. Similarly, asupply air temperature signal is received. This provides the temperatureof the air exiting the HVAC unit, after it has been processed by theHVAC unit. In most embodiments, the return air temperature will behigher than that of the supply air temperature. The temperatureinformation from the sensors may be stored and may be used at a latertime for analysis. The HVAC units may be configured in certainembodiments to control the fans and cooling valves partly based on thehistorical temperature values received at each HVAC unit.

In certain embodiments, a user's inputs may also be received, includingvarious setpoint temperatures, which may be used to control theoperations of each HVAC unit in operation. For example, the supply airsetpoint temperatures and return air supply setpoint temperatures may beinputted by users of the units and may be stored at each unit. In thepreferred embodiment, each unit's supply air temperature will be set tothe temperature the user wishes to operate the room and the return airsetpoint will be set at some degrees above the actual return temperatureof the specific HVAC unit, such as one degrees. Other information may beinputted and stored, including the fan minimum setpoint percentage, thefan ramping rate and the cooling valve ramping rate. The fan minimumsetpoint percentage is the minimum speed in which the fan may operate,as determined by a user. This value may be the optimal energy efficientvalue that the fan of each HVAC unit may operate. For example, incertain embodiments, this value may be 70 percent of the maximumcapacity of the fan. The fan ramping rate and the cooling valve-openingrate values determine the rate in which the fans' speed will beincreased and the rate in which the cooling valve will be opened whenthe HVAC units are operating to cool the return air's temperature. Forexample, the fan ramping rate may determine how much faster the fanspeed will increase per minute while the room's temperature is higherthan desired. Similarly, the cooling valve-opening rate may determinethe rate at which the valve will further open per minute while theroom's temperature is higher than desired.

At step 108, the return air temperature is compared with that of thesupply air temperature. In one preferred embodiment, the return airtemperature is first compared with a predetermined return air setpointtemperature, configurable by a user of the system. When the return airtemperature exceeds that of this return air setpoint temperature, acooling valve drive signal is generated. Similarly, the supply airtemperature is compared with a predetermined supply air setpointtemperature, also configurable by a user of the system. When the supplyair temperature is higher the supply air setpoint temperature, then acooling valve drive signal is also generated. The generated drivesignals are then compared. The higher of the drive signals, which is thesignal that requires the cooling valve to open to the greater capacity,is then used to operate the cooling valve accordingly. In oneembodiment, the larger of the differential between the actualtemperature and the setpoint temperature may be used to generate acooling valve drive signal and to control the cooling valve. In anotherembodiment, a drive signal is generated whenever the return airtemperature is not equal to that of the return air setpoint temperatureand, likewise, when the supply air temperature is not equal to that ofthe supply air setpoint temperature. Other methods of comparisons of thereturn air and supply air temperature are well within the scope of thepresently disclosed invention. In certain embodiments, the drive signalsfrom the return air supply may have a higher priority in controlling thecooling valve, or vice versa. In such cases, the drive signal generatedfrom the supply air comparisons may need to be greater by a certainpercentage or amount before it may be used to control the cooling valve.The results of the comparisons, in turn, cause the cooling valve tooperate according to a predetermined manner.

At step 116, while the cooling valve is controlled according to thereceived temperature sensor signals, the fan of the HVAC unit iscontrolled to operate at a minimum speed, such as that speed set by thefan minimum setpoint percentage. In certain embodiments, this entailsoperating the fan at the most power-efficient speed. Thus, the fan maybe controlled to operate at, for example, 70 percent of its maximumcapacity. In other embodiments, this entails operating minimally, suchas 10 percent of the fan's capacity.

Thus, the cooling valve is used to maintain the temperature of a roomwith varying conditions, all the while maintaining the fan speed at aminimum in order to save power. By only changing the cooling valve inresponse to the room's conditions and keeping the fan speed constant,load hopping may be avoided, as the unit does not attempt to cool theroom by constantly adjusting two independent variables.

In certain instances, the controlling of the cooling valves alone willnot be sufficient to lower the temperature of a room. In many instancesin which the room's temperature is too high, the complete opening of thecooling valve to 100 percent capacity will be insufficient to lower thetemperature of the room. In these instances, the HVAC units areconfigured to control the fans in response. At step 120, recognizingthat that the cooling valve has been operating at maximum capacity for apredetermined amount of time, the fan's speed will be increased aboveits predetermined minimum. The fan speed will then begin to increaseuntil the cooling valve is no longer operating at 100 percent. Incertain embodiments, the optimal speed to cool the temperature of theroom will be determined and the fan will operate at that above-minimumspeed for a predetermined amount of time before the fan speed isrecalculated again. In most cases, the fan speed will operate above theminimum speed until the return and supply air temperature signals nolonger cause the cooling valve to operate at 100 percent capacity. Whenthe cooling valve begins to operate below full capacity, the fan may beautomatically controlled to resume operating at the minimum speed, suchas 70 percent. In another embodiment, the fan will reduce its speedslowly at a predetermined rate until it reaches its minimum speed. Thismay ensure an overshooting of cooling reduction, which would cause thetemperature of the room to increase above the setpoints again.

Embodiments of the presently disclosed invention may be used incommercial or large residential environments, or any other large areasof space requiring multiple HVAC units and/or strict temperaturemaintenance. In one particular preferred embodiment, the presentlydisclosed invention is used in a computer room to maintain the airtemperature of the computer systems contained therein.

A floor plan of a data center 200 containing such a system is depictedin FIG. 2. Such a system, known in the industry as a Computer Room AirConditioning (CRAC) System, may be used in data centers that span acrosshundreds of acres of land and, yet, require the temperature to bemaintained for each individual server. In the depicted exemplary datacenter 200, there is a plurality of HVAC units 202, 202′ spaced evenlythroughout the floor. In this configuration, the units are positionedbased on the placement of the servers on the floor. As depicted in FIG.2, there may be a plurality of servers 204, 204′ stored in rows ofserver racks and a plurality of HVAC units that are placed along thewalls of the room. Thus, there may be a plurality of HVAC units, eachresponsible for one or more servers 204, 204′. Each HVAC unit 202, 202′,is responsible for maintaining the temperature of the area physicallylocated near it by cooling, heating, humidifying, or dehumidifying theair. It is advantageous and desirable to have more than one HVAC unitresponsible for each area on the server floor for redundancy purposes.This ensures that temperatures of each area may be maintained even whenone HVAC unit fails to operate or malfunctions, thereby ensuring, atleast temporarily, the avoidance of server failures.

In certain embodiments of the CRAC system, servers 204, 204′ arepositioned on a floor that has been raised, providing space for air tobe ventilated underneath the floor. Each CRAC unit receives thehigher-temperature air above the floor, processes and cools the airthrough cooling means and procedure described in more details below withrespect to each unit, and releases the cooler air underneath the raisedfloor. The cooler air travels throughout the space underneath the raisedfloor and is released through vents or other ventilation means wellknown in the art through the floors including directly underneath theserver racks. Thus, this creates an airflow system wherein hot airproduced at servers and server racks are cooled as necessary.

In embodiments of the presently disclosed invention, the individual HVACunits 202, 202′ are not controlled by a central controller or computer.Instead, each unit operates independently to maintain the air near eachunit. This manner of operation is common for HVAC systems that are usedin commercial and residential spaces and is especially common for CRACsystems. Each unit may be individually programmed or controlled by acomputer that is connected to or is part of each HVAC unit.

In another embodiment, the individual CRAC units may be connected to acentral computer, which may then be controlled by the central computer.As shown in FIG. 3, the individual HVAC units 302, 302′, and 306 of thesystems may be connected to a central computer 310. This centralcomputer 310 may have the capability to program each of the HVAC units302, 302′, and 306 to act in any manner as desired. The central computermay control the fan speed or the cooling valve opening of each unit,according to the signals received from each unit's return airtemperature sensor and the supply air temperature. Thus, in such asystem, the return and supply setpoint temperature may be controlled bythe central computer 316. In other embodiments of the presentlydisclosed invention, the central computer may be configured to set andautomatically change setpoint temperatures of certain HVAC units basedon processing load of a server 304. Thus, for example, when a server 308of the system is processing a large number of requests or tasks suchthat the server 308's processor began to operate at a higher frequencyand the overall temperature of the server 308 and the surrounding areabegan to increase, the central computer 310 may automatically controlthe HVAC units' cooling valves and/or fans. In these embodiments, theserver 304, 304′ and 308 may be connected to the central computer 310(connection not shown). When the processing load of a server begins toincrease or reaches a certain predetermined level, the central computer310 may receive a signal from server 308 or detect the high load of theserver 112 automatically. In response, the central computer 310, mayanticipate any change in temperature of the area surrounding server 308and may cause the CRAC unit 306, which is a unit known to be near server308, to began to cool the area, such as by changing the setpointtemperature of the HVAC unit 306 such that the cooling valves are openedfurther and the temperature of the air supplied from the HVAC unit islowered.

The depicted data centers 200 and 300 represent an exemplaryillustration and a plurality of other components may be added orexisting components may be removed or modified without departing fromthe scope of the invention. The data centers 200 and 300 may include anynumber of racks and various other apparatuses known to be housed in datacenters. Thus, although the data centers 200 and 300 are illustrated ascontaining five rows of servers, it should be understood that the datacenters 200 and 300 might include any number of servers and server rackswithout departing from the scope of the invention. The depictedconfigurations of the servers in data centers 200 and 300 are thus forillustrative purposes only and are not intended to limit the inventionin any respect. In addition, the data center 200 and 300 may include anynumber of HVAC units 204, 204′, 302, 302′ and 306, each having a numberof different types of cooling systems, such as those described in detailbelow.

A block diagram of an exemplary HVAC unit is depicted in FIG. 4. Theunit 400, which may contain a plurality of other components not shown,may comprise at least one return air sensor 412, at least one supply airsensor 408, a computer 404, a fan controller 416 and a cooling valvecontroller 420.

Each HVAC unit may contain or may be connected to a plurality ofsensors. Specifically, each HVAC unit may contain or may be connected toone or more return air temperature sensors 412 and one or more supplyair temperature sensors 408. Each sensor has the capability to send anelectronic signal back to the computer 404 with the current temperature.The transmission of signals may occur automatically on a predeterminedschedule, such as every 10 to 15 seconds, or it may occur upon requests.In certain other embodiments, the sensors may further have the abilityto store a history of received sensor data. The temperature sensors 408,412 may be physically located on or immediately near each HVAC units. Inanother embodiment, they may be located remotely from each HVAC unit andmay communicate the information to each respective HVAC unit via wiredor wireless communication means, including, but not limited to radio,Wi-Fi, cellular, Bluetooth, and other means well known in the art. Thesensors may also be located on or near the various servers such asbetween the server racks.

The supply air sensor 408 may be positioned at an outlet of the unit andis thus configured to measure one or more conditions of the coolingfluid supplied by the unit. Alternatively, the sensors 408, 412 may bepositioned at an inlet of a server or a server rack or near a floorvent, provided that servers, racks or the vent tile is located within aproximity to the exhaust of HVAC unit. The supply air temperature sensormay be positioned at a location substantially downstream of the unitwhere the temperature of the cooling fluid supplied by the unit does notvary beyond a certain level from the time the cooling fluid exits theunit. The return air temperature sensor, similarly, may be placed at theinlet of the HVAC unit, such as where the air is received at or withinthe unit prior to the air's processing/cooling by the HVAC unit. Inanother embodiment, the return air temperature sensor 412 is placed at alocation remote from the HVAC unit, such as at a position within theroom's airflow just prior to its receipt by the HVAC unit. The ideallocation for such sensors may differ based on configuration of thecomputer room. One of ordinary skill in the art may determine the ideallocation based on the room's configuration such that the temperature ofthe servers may be adequately measured, including adequately measuringor determining the existence of any pockets of air that is of highertemperature than its surroundings. Overlapping sets of sensors may beused to control respective HVAC units to account for the couplingeffects of multiple HVAC units on a common controlled space. Embodimentscan also ensure that the spatial variation of the controlledenvironmental variables is minimized, thereby increasing efficiency andproviding a comfortable and uniform temperature in the environment. Inaddition to these sensors, there may be a plurality of other types ofsensors including sensors that measure the humidity, pressure, and otherenvironmental conditions.

Information from the various sensors is received at a computer 404located at each HVAC unit. The computer 404 may comprise a computersystem, a controller, microprocessor, etc., configured to controloperations of the HVAC units. More particularly, the computer 404 may beconfigured to receive input from the return air temperature and/or thesupply air temperature sensors and to vary the operations of the variousvariable controllable systems contained in the HVAC units. The computer404 may also be configured to receive inputs from a user of the systemsuch as data center personnel, an administrator, a manager, or others.The input received from a user may comprise various setpoints by whichthe computer 404 may determine how and when to manipulate the operationsof the variable control system. The computer 404 may, for example,compare the temperature, humidity, pressure, and other informationdetected by the sensors with predetermined setpoints for thoseconditions and control the variable control system in response todifferences between the setpoints and the detected conditions. Thus, inthe preferred embodiments, the system may store, temporarily orpermanently, supply air temperature setpoints and return air supplytemperature setpoints. Other information that the system may storeincludes fan minimum setpoint percentage, the fan ramping rate and thecooling valve span ramp rate.

Computers typically include a variety of computer readable media thatcan form part of the system memory and be read by the processing unit.By way of example, and not limitation, computer readable media maycomprise computer storage media and communication media. The systemmemory may include computer storage media in the form of volatile and/ornonvolatile memory such as read only memory (ROM) and random accessmemory (RAM). A basic input/output system (BIOS), containing the basicroutines that help to transfer information between elements, such asduring start-up, is typically stored in ROM. RAM typically contains dataand/or program modules that are immediately accessible to and/orpresently being operated on by processing unit. The data or programmodules may include an operating system, application programs, otherprogram modules, and program data. The operating system may be orinclude a variety of operating systems such as Microsoft Windows®operating system, the Unix operating system, the Linux operating system,the Xenix operating system, the IBM AIX™ operating system, the HewlettPackard UX™ operating system, the Novell Netware™ operating system, theSun Microsystems Solaris™ operating system, the OS/2™ operating system,the BeOS™ operating system, the Macintosh™® operating system, theApache™ operating system, an OpenStep™ operating system or anotheroperating system of platform.

At a minimum, the memory includes at least one set of instructions thatis either permanently or temporarily stored. The processor executes theinstructions that are stored in order to process data. The set ofinstructions may include various instructions that perform a particulartask or tasks, such as those shown in the appended flowcharts. Such aset of instructions for performing a particular task may becharacterized as a program, software program, software, engine, module,component, mechanism, or tool. The computer 400 may include a pluralityof software processing modules stored in a memory as described above andexecuted on a processor in the manner described herein. The programmodules may be in the form of any suitable programming language, whichis converted to machine language or object code to allow the processoror processors to read the instructions. That is, written lines ofprogramming code or source code, in a particular programming language,may be converted to machine language using a compiler, assembler, orinterpreter. The machine language may be binary coded machineinstructions specific to a particular computer.

Any suitable programming language may be used in accordance with thevarious embodiments of the invention. Illustratively, the programminglanguage used may include assembly language, Ada, APL, Basic, C, C++,COBOL, dBase, Forth, FORTRAN, Java, Modula-2, Pascal, Prolog, REXX,and/or JavaScript for example. Further, it is not necessary that asingle type of instruction or programming language be utilized inconjunction with the operation of the system and method of theinvention. Rather, any number of different programming languages may beutilized as is necessary or desirable.

In addition, the instructions and/or data used in the practice of theinvention may utilize any compression or encryption technique oralgorithm, as may be desired. An encryption module might be used toencrypt data. Further, files or other data may be decrypted using asuitable decryption module.

The computer receives the data from the sensors 408, 412 and variousother sources. Based on this information and the logic or computerprogram instructions stored at the computer, it controls a plurality ofdevices including at least one fan and at least one cooling valve. Asseen in FIG. 4, the computer 404 is connected to a fan controller 416and a cooling valve controller 420 via a data bus. By transmittingsignals to the fan controller fan controller 416 and cooling valvecontroller 420, the computer controls the speed and output of the fansand cooling valves. The connection may also allow the computer toreceive various parameter data from the fans and/or cooling valves suchas the conditions of the fan and any filters. The computer 404 mayadditionally receive various alarm signals from the fan controller 416and the cooling valve controller 420 including any water leak alarm,critical alarm, controller alarms, and general alarms.

The fan controller 416 may contain or may be connected to a variablespeed drive (VSD) that operates to control the fan to vary the volume ofcooling flow that is flowing into and out of the HVAC unit 400. The VSD,which may also be known as a variable-frequency drive (VFD),adjustable-frequency drive (AFD), AC drive, microdrives, and inverterdrives, is widely used in ventilation systems and may comprise anyreasonably suitable VSD that is commercially available from any numberof manufacturers. The VSD generally operates to control the speed of analternating current (AC) induction motor by converting power from fixedvoltages/fixed frequencies to variable voltages/variable frequencies. Bycontrolling the voltage/frequency levels of the fan, the flow rate ofthe cooling fluid supplied by each HVAC unit may also be variedaccordingly. Thus in the disclosed systems, the computer 404 has thecapability to control the voltage frequency level variably according tothe instructions stored at the computer 404.

The cooling valve controller 420 may be connected to one or more valvesthat may be variably opened or closed to a controllable percentage. Thecooling valve is a fluid bypass that allows a small amount of fluid tocontinuously enter the valve inlet, pass through the chamber of thevalve, then out of the valve.

In operation, heated air enters into the HVAC unit 400 from the datacenter. It bypasses a filter and is cooled by the lower-temperaturewater entering the HVAC unit, as controlled by the cooling valve. Thetemperature of the water entering the units may be controlled and may beset at some predetermined level, such as 21 degrees Celsius. To controlthe temperature of the air exiting the HVAC unit, the cooling valve maybe opened wider or narrower as necessary, which then results in more orless cool water flowing through the HVAC unit, thereby cooling the airto a controllable temperature. The fan may then be controlled todetermine how much air is passed through the HVAC units.

In one embodiment, the hot air is cooled by operation of a cooling coil,a compressor, a condenser, and an expansion valve, which may operateunder a vapor-compression cycle. A refrigerant may be contained in arefrigerant line and may be supplied into the cooling coil, resulting inthe absorption of heat of the received hot air through convection. Thecooled cooling air then flows out of the HVAC unit.

In some environments, heat may be necessary to maintain the temperatureof a data room at an optimal level. In these cases, heated refrigerantis used and is flowed into the compressor, which is then flowed into thecondenser where some of the heat in the refrigerant is dissipated intothe air around the data center. The condenser may also include a fan todissipate and spread the heat in a manner similar to that of the coolingsystems. The refrigerant then flows through the expansion valve and backthrough the cooling coil. This process may be continuously repeated tocool the cooling fluid drawn into the HVAC unit.

In order to optimally maintain the temperature of a data center or otherlarge environments requiring multiple HVAC units, the presentlydisclosed HVAC system contains executable program instructions that,when executed, operate to control the fan speed and cooling valves basedon the information received from both the return air temperature and thesupply air temperature sensors.

In particular, each unit will be controlled based on the informationreceived from the return air temperature sensor and the supply airtemperature as well as the information stored at the computer 404,including the supply air setpoint, the return air setpoint, the fanminimum setpoint percentage, the fan ramping rate, and the cooling valveramping rate. The supply air setpoint and the return air setpoint areuser customizable temperature values that, when compared with thecorresponding return air temperature and the supply air temperature,determine the control signals transmitted by the computer 404. The fanminimum setpoint percentage, which is also customizable by the user, isthe minimum speed in which the fan will operate. This value may be theoptimal energy efficient values that each HVAC unit may operate. Forexample, in one embodiment, this value may be 70 percent. In otherwords, the fan of these HVAC units will operate, at a minimum at 70percent of its maximum output. Finally, the fan ramping rate and thecooling valve-opening rate determine the rate in which the fans willincrease their speed and valve openings in the HVAC unit's attempt tolower or increase the temperature of a room. For example, fan rampingrate may determine how much faster the fan speed will increase for every3 minutes in which the room's temperature is higher than desired.Similarly, the cooling valve-opening rate may determine the percentagein which the valve opening will open further for every 5 minutes inwhich the room's temperature is higher than desired. While a certaintime parameter is used in these examples, they are for exemplarypurposes only and may be customizable by the users. Furthermore, thecomputer may only increase (or decrease) fan speed and valve openingunder certain circumstances, as explained in detail below.

In the preferred embodiment, each unit's supply air temperature will beset to the temperature the user wishes to operate the data room. Thus,when the supply air temperature is higher than the desired supply airsetpoint, the computer 404 will transmit a drive signal to the coolingvalve controller 400 to open the cooling valve at the coolingvalve-opening rate until the supply air temperature meets that of thesupply air setpoint temperature. In one embodiment, this will be set at18 degrees Celsius.

The return air setpoint may be set to one Celsius degree above theactual return temperature of the specific HVAC unit. Further, the fanminimum setpoint percentage will be set at 70 percent. Thus, inoperation, the presently disclosed HVAC unit's computer 404 willtransmit control signals to the fan controller 416 to operate the fan at70 percent. In other embodiments, the fan minimum setpoint percentagewill bet set higher or lower than 70 percent, depending on the fan'smost power efficient rate of operation.

In order to save energy and to operate efficiently, each HVAC unit ofthe presently disclosed invention is configured to maintain thetemperature of a room, first, by use of the cooling valve, and secondand only when the capacity of the cooling valve has peaked, by use ofthe fan. In other words, each computer 404 is configured to maintain thefan speed at the fan minimum setpoint percentage until the cooling valveis operating at maximum capacity.

FIG. 5 illustrates this method of maintaining the temperature of theroom in more detail. In particular, the computer 404 will receive thereturn air temperature signal and the supply air temperature signal fromthe return air sensor 412 and the supply air sensor 408, as seen in step500. In one embodiment, this receiving of the temperature signals iscontinuous and in-real time. In another embodiment, the computer 404will receive the temperature signals at predetermined intervals or mayreceive the temperature on demand. The return air temperature and thereturn air setpoint temperature is compared at each instance in whichthe return air temperature signal is received, as shown in step 502 and506. Similarly, at step 504 and 508, the supply air temperature iscompared with the supply air setpoint temperature at each instance inwhich the supply air temperature signal is received by computer 404.

When the return air temperature exceeds that of the return air setpointtemperature, the computer 404 generates a cooling valve drive signalthat operates at the cooling valve to open to a specific percentage orvalue, as seen at step 510. Similarly, when the supply air temperatureexceeds that of the supply air setpoint, the computer, at step 512,calculates and generates a cooling drive signal that also operates atthe cooling valve to open to a specific percentage or value. In anotherembodiment, a drive signal is generated whenever the return airtemperature is not equal to that of the return air setpoint temperatureand, likewise, when the supply air temperature is not equal to that ofthe supply air setpoint temperature. Other methods of comparisons of thereturn air and supply air temperature are well within the scope of thepresently disclosed invention. In certain embodiments, the drive signalsfrom the return air supply may have a higher priority in controlling thecooling valve, or vice versa. In such cases, the drive signal generatedfrom the supply air comparisons may need to be greater by a certainpercentage or amount before it may be used to control the cooling valve.

In the presently disclosed invention, which uniquely takes intoconsideration both the return air temperature and the supply airtemperature, the computer 404 is further configured, in its control ofthe cooling vale control 420 and therefore the cooling valve, to comparethe two cooling valve drive signals at step 514. It will then determinethe higher of the two drive signals and, as shown at step 516, transmita control signal to the cooling valve controller 420 to operate thecooling valve according to the higher drive signal. Any methods wellknown in the art may be used to determine the higher of the two signals.For example, the higher signal may be the signal that requires thecooling valve to open at the greater percentage. In one embodiment, thelarger of the differential between the actual temperature and thesetpoint temperature may be used to control the cooling valve. Incertain embodiments, the comparison of the drive signals generated atthe computer 404 in response to 1) the return air temperature andsetpoint, and 2) the supply air temperature and setpoint, takes place atthe cooling valve controller 420. In either case, the cooling valve isopened at a certain rate based on the received drive signal. In oneembodiment, the computer is configured to further determine whether thecooling valve is already operating at maximum capacity, as seen in step520. If it is not, the computer 404 is configured to restart theprocess. Similarly, when the return air temperature is less than orequal to the return air temperature setpoint or when the supply airtemperature is less than or equal to the supply air temperaturesetpoint, the computer 404 is configured to restart the process ofreceiving the return and supply air temperature at step 500. In certainembodiments, the method does not begin for a predetermined period oftime, such as 1 minute.

Thus, the presently disclosed HVAC units will continue to control thecooling valves by increasing or decreasing the cooling valve's openingas necessary to maintain the temperature of the room according to thesetpoints. However, in certain instances, the controlling of the coolingvalves alone, will not be sufficient to lower the temperature of a room.In particular, in many instances in which the heat created by theservers is too great, the cooling valve will be opened to 100 percentcapacity without any effects in lowering the temperature of the room.Thus, as seen at step 520 of FIG. 5, the computer 404 will detect thatthe cooling valve is operating a maximum capacity. In these instances inwhich the cooling valve is operating at full capacity, the computer 404is configured to, then, increase the speed of the fan from the minimumsetpoint percentage. The computer 404, recognizing that that the coolingvalve has been operating at maximum capacity for a predetermined amountof time, at step 522, generates and transmits a fan control signal thatoperates at the fan speed controller to increase the speed of the fansaccording to the predetermined fan ramping rate. The fan speed will thenbegin to increase according to the fan ramping rate. In one embodiment,the computer 404 will determine optimal speed to operate the fan inorder to cool the temperature of the air in a predetermined amount oftime. The fan may operate at that speed for a predetermined amount oftime before recalculating the necessary optimal speed to operate. Inmost cases, the fan will operate above the minimum setpoint percentageuntil neither of the cooling valve drive signals that are generated atthe computer 404 are operating the cooling valve at 100 percentcapacity. When the cooling valve begins to operate below full capacity,the computer may automatically transmit a signal to the fan speedcontroller 416 to resume operating at the minimum setpoint percentage,such as 70 percent (step not shown). In another embodiment, when thecomputer 404 will simply reduce the fan's speed, but nonetheless,maintain the speed above the minimum setpoint percentage for apredetermined amount of time. This may ensure an overshooting of coolingreduction, which would cause the temperature to increase above thesetpoints again.

After it transmits the drive signals to the fan and/or cooling valvecontroller, the process is restarted and the computer begins to receivethe return air temperature signal and supply air temperature signalagain to adjust the cooling valves and fans as necessary to maintain thetemperature and condition of the room as desired. The process may notbegin until after a predetermined period of time in certain embodiments.

The components depicted and described herein above may be or include acomputer or multiple computers. Although the components are shown asdiscrete units, all components may be interconnected or combined. Thecomponents may be described in the general context ofcomputer-executable instructions, such as program modules, beingexecuted by a computer. Generally, program modules include routines,programs, objects, components, data structures. etc. that performsparticular tasks or implement particular abstract data types.

Those skilled in the art will appreciate that the invention may bepracticed with various computer system configurations, includinghand-held wireless devices such as mobile phones or PDAs, multiprocessorsystems, microprocessor-based or programmable consumer electronics,minicomputers, mainframe computers, and the like. The invention may alsobe practiced in distributed computing environments where tasks areperformed by remote processing devices that are linked through acommunications network. In a distributed computing environment, programmodules may be located in both local and remote computer storage mediaincluding memory storage devices.

The computing environment may also include other removable/nonremovable,volatile/nonvolatile computer storage media. For example, a hard diskdrive may read or write to nonremovable, nonvolatile magnetic media. Amagnetic disk drive may read from or writes to a removable, nonvolatilemagnetic disk, and an optical disk drive may read from or write to aremovable, nonvolatile optical disk such as a CD ROM or other opticalmedia. Other removable/nonremovable, volatile/nonvolatile computerstorage media that can be used in the exemplary operating environmentinclude, but are not limited to, magnetic tape cassettes, flash memorycards, digital versatile disks, digital video tape, solid state RAM,solid state ROM, and the like. The storage media are typically connectedto the system bus through a removable or nonremovable memory interface.

The processing unit that executes commands and instructions may be ageneral purpose computer, but may utilize any of a wide variety of othertechnologies including a special purpose computer, a microcomputer,mini-computer, mainframe computer, programmed micro-processor,micro-controller, peripheral integrated circuit element, a CSIC(Customer Specific Integrated Circuit). ASIC (Application SpecificIntegrated Circuit), a logic circuit, a digital signal processor, aprogrammable logic device such as an FPGA (Field Programmable GateArray), PLD (Programmable Logic Device), PLA (Programmable Logic Array),RFID processor, smart chip, or any other device or arrangement ofdevices that is capable of implementing the steps of the processes ofthe invention.

It should be appreciated that the processors and/or memories of thecomputer system need not be physically in the same location. Each of theprocessors and each of the memories used by the computer system may bein geographically distinct locations and be connected so as tocommunicate with each other in any suitable manner. Additionally, it isappreciated that each of the processor and/or memory may be composed ofdifferent physical pieces of equipment.

A user may enter commands and information into the computer through auser interface that includes input devices such as a keyboard andpointing device, commonly referred to as a mouse, trackball or touchpad. Other input devices may include a microphone, joystick, game pad,satellite dish, scanner, voice recognition device, keyboard, touchscreen, toggle switch, pushbutton, or the like. These and other inputdevices are often connected to the processing unit through a user inputinterface that is coupled to the system bus, but may be connected byother interface and bus structures, such as a parallel port, game portor a universal serial bus (USB).

One or more monitors or display devices may also be connected to thesystem bus via an interface. In addition to display devices, computersmay also include other peripheral output devices, which may be connectedthrough an output peripheral interface. The computers implementing theinvention may operate in a networked environment using logicalconnections to one or more remote computers, the remote computerstypically including many or all of the elements described above.

Various networks may be implemented in accordance with embodiments ofthe invention, including a wired or wireless local area network (LAN)and a wide area network (WAN), wireless personal area network (PAN) andother types of networks. When used in a LAN networking environment,computers may be connected to the LAN through a network interface oradapter. When used in a WAN networking environment, computers typicallyinclude a modem or other communication mechanism. Modems may be internalor external, and may be connected to the system bus via the user-inputinterface, or other appropriate mechanism. Computers may be connectedover the Internet, an Intranet, Extranet, Ethernet, or any other systemthat provides communications. Some suitable communications protocols mayinclude TCP/IP, UDP, or OSI for example. For wireless communications,communications protocols may include Bluetooth, Zigbee, IrDa or othersuitable protocol. Furthermore, components of the system may communicatethrough a combination of wired or wireless paths.

Although many other internal components of the computer are not shown,those of ordinary skill in the art will appreciate that such componentsand the interconnections are well known. Accordingly, additional detailsconcerning the internal construction of the computer need not bedisclosed in connection with the present invention.

The various embodiments and features of the presently disclosedinvention may be used in any combination as the combination of theseembodiments and features are well within the scope of the invention.While the foregoing description includes many details and specificities,it is to be understood that these have been included for purposes ofexplanation only, and are not to be interpreted as limitations of thepresent invention. It will be apparent to those skilled in the art thatother modifications to the embodiments described above can be madewithout departing from the spirit and scope of the invention.Accordingly, such modifications are considered within the scope of theinvention as intended to be encompassed by the following claims andtheir legal equivalent

The presently disclosed invention improves upon known methods andsystems of controlling HVAC systems by controlling the systems tooperate more efficiently, thereby saving energy. One manner in which themethod and system saves energy is through the prevention of loadhopping. As previously discussed, “load hopping,” which is whenneighboring HVAC units will alternately run at full capacity while itsneighbors sit inactive, results in tremendous power consumption andinefficiency. By operating in the method described, taking intoconsideration not only the temperature of the supply air but also thetemperature of the return air, load hopping is prevented. The systemfurther prevents CRAC unit component failures. By taking intoconsideration the return air temperature (as well as the supply airtemperature) and by prioritizing cooling options that are powerefficient, the various HVAC units in a system efficiently operateaccording to the changing environmental conditions. Moreover, when aHVAC unit fails, the computer 404 of the surrounding neighboring unitswill automatically recognize the higher return air temperature. Thecomputers 404 will then operate to lower the room temperature to thedesired setpoint by compensating for the lost cooling capacity. Thedisclosed invention may reduce as much as 25 percent of current energyconsumption, which may be even greater depending on exteriorenvironmental factors. As a result, the presently disclosed inventionmay have dramatic positive effects by reducing fossil fuel consumptionand greenhouse gas emissions. It further may save corporations millionsof dollars in annual power costs.

1-20. (canceled)
 21. A method for configuring a plurality of heating,ventilation, and air conditioning (HVAC) systems, the systems includingat least one control circuit, the method comprising: receiving a firstreturn air temperature signal at a control circuit from a first HVACunit; receiving a first supply air temperature signal at the controlcircuit from the first HVAC unit; controlling fans and cooling valves oftwo or more HVAC units of the plurality of HVAC systems, based at leaston the received first return air temperature signal, the first receivedsupply air temperature signal, a return setpoint temperature, and asupply setpoint temperature.
 22. The method of claim 21, furthercomprising the steps of: receiving a second return air temperaturesignal at a control circuit from a first HVAC unit; receiving a secondsupply air temperature signal at the control circuit from the first HVACunit; controlling the fans and the cooling valves of two or more HVACunits of the plurality of HVAC systems, based at least on the secondreceived return air temperature signal, the second received supply airtemperature signal, a return setpoint temperature, and a supply setpointtemperature.
 23. The method of claim 22, further comprising the step ofcontrolling a fan and the cooling valve of second HVAC unit of theplurality of HVAC systems based at least on the second received returnair temperature signal, the second received supply air temperaturesignal, the first received return air temperature signal and the firstreceived supply air temperature.
 24. The method of claim 21, wherein thefans of two or more HVAC units are controlled according to at least afan ramping rate and the cooling valves of the two or more HVAC unitsare controlled according to at least a cooling valve opening rate. 25.The method of claim 21, further comprising: generating a cooling valvedrive signal according to at least one of return air temperature signaland supply air temperature signal.
 26. The method of claim 21,comprising: generating a first cooling valve drive signal based on acomparing of the return temperature signal and a return setpointtemperature; generating a second cooling valve drive signal based on acomparing of the supply temperature signal and a supply setpointtemperature.
 27. The method of claim 26, wherein the controlling of thecooling valves is based on a comparison of a priority associated withthe first cooling valve drive signal and a priority associated with thesecond cooling valve drive signal.
 28. The method of claim 21, whereinthe controlling step further comprises: controlling the fans to operateat a minimum speed based on a capacity of the cooling valve.
 29. Themethod of claim 21, wherein the controlling step further comprises:controlling the fans to operate above a minimum speed based on thecooling valve operating at a maximum capacity.
 30. The method of claim21, wherein the controlling step further comprises controlling thecooling valves to operate at a minimum capacity based on comparing thereturn air temperature signal with a cooling valve setpoint temperature.31. The method of claim 21, wherein the controlling of the fans and thecooling valves is based on at least one of humidity and air pressure.32. A heating, ventilation, and air conditioning (HVAC) system, thesystem comprising: a plurality of HVAC units, each HVAC unit including:at least one fan; at least one cooling valve; and a processor, saidprocessor coupled to the least one fan and the at least one coolingvalve; and a control circuit, the control circuit is adapted to executeinstructions to perform the following: receiving a first return airtemperature signal at a control circuit from a first HVAC unit;receiving a first supply air temperature signal at the control circuitfrom the first HVAC unit; controlling fans and cooling valves of two ormore HVAC units of the plurality of HVAC systems, based at least on thereceived first return air temperature signal, the first received supplyair temperature signal, a return setpoint temperature, and a supplysetpoint temperature.
 33. The system of claim 32, wherein the controlcircuit is adapted to execute instructions to further perform thefollowing: receiving a second return air temperature signal at a controlcircuit from a first HVAC unit; receiving a second supply airtemperature signal at the control circuit from the first HVAC unit;controlling the fans and the cooling valves of two or more HVAC units ofthe plurality of HVAC systems, based at least on the second receivedreturn air temperature signal, the second received supply airtemperature signal, a return setpoint temperature, and a supply setpointtemperature.
 34. The system of claim 33, wherein the control circuit isadapted to execute instructions to control a fan and the cooling valveof second HVAC unit of the plurality of HVAC systems based at least onthe second received return air temperature signal, the second receivedsupply air temperature signal, the first received return air temperaturesignal and the first received supply air temperature.
 35. The system ofclaim 32, wherein the fans are controlled according to at least a fanramping rate and the cooling valves are controlled according to at leasta cooling valve opening rate.
 36. The system of claim 32, the controlcircuit is further adapted to execute instructions to generate a coolingvalve drive signal according to at least one of return air temperaturesignal and supply air temperature signal.
 37. The system of claim 32,the control circuit is further adapted to execute instructions toperform the following: generating a first cooling valve drive signalbased on a comparing of the return temperature signal and a returnsetpoint temperature; generating a second cooling valve drive signalbased on a comparing of the supply temperature signal and a supplysetpoint temperature.
 38. The system of claim 37, wherein thecontrolling of the cooling valves is based on a comparison of a priorityassociated with the first cooling valve drive signal and a priorityassociated with the second cooling valve drive signal.
 39. The system ofclaim 32, the control circuit's controlling of the fan and the coolingvalves further comprises: controlling a fan to operate at a minimumspeed based on a capacity of the cooling valve.
 40. The system of claim32, the control circuit's controlling of the fans and the cooling valvesfurther comprises controlling a fan to operate above a minimum speedbased on the cooling valve operating at a maximum capacity.
 41. Thesystem of claim 32, the control circuit's controlling of the fans andthe cooling valves further comprises controlling a cooling valve tooperate at a minimum capacity based on comparing the return airtemperature signal with a cooling valve setpoint temperature.
 42. Thesystem of claim 32, wherein the controlling of the fans and the coolingvalves is based on at least one of humidity and air pressure.